1. Field of the Invention
The present invention relates generally to a dispensing device for dispensing a multi-component composition such as, for example, epoxy cements, adhesives, medicaments, and dental materials. More particularly, the invention relates to a dispensing syringe having a syringe body with at least two elongated barrels. Each barrel is used to store and dispense a component of the composition. The dispensing syringe may include a dispensing tip containing a static mixing element for mixing the components and then dispensing the mixed composition. Preferably, the syringe is used to mix and dispense a dental composition such as, for example, a dental cement or adhesive.
2. Brief Description of the Related Art
Dental professionals use dispensing syringes for storing, mixing, and dispensing a wide variety of dental compositions. For instance, a dentist may use a dispensing syringe in preparing and dispensing dental impression materials, temporary restorative materials, cements and adhesives. Such dental compositions can be self-curable, light-curable, or dual-curable. The dental compositions are cured and hardened by different chemical mechanisms to form a strong and durable material. In one example, a dentist uses a self-curing dental cement, which is prepared from two paste components, for bonding crowns, bridges, veneers, and other restoratives to the tooth. Generally, about 0.25 to about 0.5 mL of dental cement is used in such applications. One component used to make the dental cement is a base paste and the other component is a catalyst paste. The base paste typically contains polymerizable monomers such as methacrylate or acrylate monomers; a free-radical polymerization accelerator such as a tertiary amine; and fillers such as silica, glasses, or alumina. Meanwhile, the catalyst paste typically includes a polymerizable monomer, a free-radical polymerization initiator such as a peroxide, and fillers.
The base and catalyst pastes can be measured and mixed together by hand or an auto-mix syringe system can be used. Dentists often prefer working with auto-mix systems, because the base and catalyst pastes are stored in commercially-available cartridges and can be dispensed from the cartridges in a pre-determined volume ratio to form an optimally mixed composition. The dentist can save time using such auto-mix systems and avoid mixing ratio errors. A “double barrel” dispensing syringe is often used in auto-mix systems. In general, the double barrel syringe includes two separate, elongated barrels or chambers that are arranged in a side-by-side configuration. The barrels are sealed, and the base paste is stored in one barrel, while the catalyst paste is stored in the other barrel. The barrels are connected to a dispensing tip. In practice, the dentist pushes on the plunger of the syringe to force the base and catalyst pastes from their respective barrels and into the dispensing tip. The dispensing tip typically contains a static mixer. As the base and catalyst pastes are extruded through the static mixer, they are combined and mixed together to form the final, mixed dental cement. Then, the dentist can dispense the cement onto the desired target, for example, a temporary crown, and mount the crown over a “crown-prepped” tooth in the mouth of the patient.
In another example, the double barrel syringe is used to dispense a dental composition used to make the temporary crown. Generally, about 1 to about 2 mL of material is used to make the temporary crown. Normally, the dentist places a temporary crown on the tooth to cover and protect the tooth, until a dental laboratory makes the permanent crown. The temporary crown is made from a polymeric material such as an acrylic. More particularly, a polymerizable material, which is prepared from base and catalyst pastes, can be used to form the temporary crown. In a manner similar to the above-described method used to make dental cements, the base and catalyst pastes are stored in the barrels of the syringe until it is time to prepare the crown. Then, the base and catalyst pastes are forced from their respective barrels and into the dispensing tip containing the static mixing element. The pastes are mixed in the dispensing tip and the resulting composition is dispensed onto an alginate impression, plastic matrix, or other material to make the temporary crown.
One example of a double barrel syringe is illustrated in Drake, U.S. Pat. No. 4,538,920. This patent discloses a dispensing device having a having a pair of chambers for storing dental resins separately and a pair of plungers that are forced into the chambers to discharge the resins. The device further includes a static-mixing element housed with an exit conduit and a discharge nozzle. The static-mixing element is held in a fixed position in order to maintain a predetermined alignment of a first blade in the static-mixing element relative to the two streams of resinous material. The patent suggests that this is necessary to achieve maximum mixing of the two streams of resinous materials in the discharge nozzle.
Spehar et al., U.S. Pat. No. 4,753,536 describes a double barrel syringe with two compartments for storing two separate dental polymeric materials, a discharge assembly, and a nozzle assembly for dispensing the material. The nozzle assembly comprises a common nozzle, a static-mixing element with an arm extending from one end. The static mixer is arbitrarily inserted into the bore of the nozzle. The discharge of the polymeric material from the compartments causes the static mixer to turn until the arm engages an end stop. The end stop prevents further rotation of the arm as material is fed into the nozzle, thereby allowing the mixer to intermix the two materials from the storage compartments.
Sawhney et al., U.S. Pat. No. 6,394,314 discloses a double-barreled syringe for storing two viscous dental substances. The syringe includes a double-plunger assembly with juxtaposed first and second plungers and a mixing tip. The plungers are attached at their distal end to a disc-shaped thumb-rest so that when the thumb-rest is depressed the plungers move forward in tandem and discharge the substances into the mixing tip. The mixing tip is detachable after the tip is locked to the syringe body, so a person can replace the tip with a locking cap.
Bills, U.S. Pat. No. 6,732,887 discloses a double barrel syringe having detachably connecting barrels, detachably connecting plungers, and an applicator tip. The barrels can be manufactured at different times and out of different materials so that they have different colors, insulating properties, and opaque or translucent properties. The plunger assembly includes a first plunger, which is pressed to force out the first component from the first barrel and a second plunger, which is pressed to force out the second components from the second barrel.
Xie et al., U.S. Pat. No. 6,843,652 describes the device as being particularly suitable for delivering a single dose quantity of a two-component dental impression material. The double barrel syringe includes a dispenser body having a first and second cylindrically shaped chamber, an actuator, a closure, and a dispenser tip. The first and second components of the material are stored in their respective chambers. The actuator includes first and second plungers, which are adapted to slide within the first and second chambers and dispense the respective components. The plungers are connected at their distal end by a thumb pad. A dental professional depresses the thumb pad when he or she is ready to dispense the material. This causes the plunger rods to move in unison and dispense the first and second components simultaneously.
In the double-barrel syringes described in the above-mentioned patents, a person must depress the syringe plunger to force the resin components from the barrels and into a mixing/dispenser tip. These double-barrel syringes are generally effective. One drawback, however, is that it can be difficult to dispense resins having a thick consistency using such conventional double-barrel syringes. A sufficient amount of pressure must be exerted on the thumb pad or other actuator handle, and it can be difficult to apply this force while handling the syringe at the same time.
Other dual chamber systems for dispensing dental material are known including hand-held ejector-type guns as described in Wilcox et al., U.S. Pat. Nos. 5,624,260 and 5,722,829. These gun-like applicators include a cartridge having a first chamber and a second chamber for storing dental materials and a pair of plungers for dispensing the materials through a discharge tip. The applicator further includes a handle extending from a body portion and an arm located next to the handle and movable relative to the body. To advance the plungers, the arm is swung about the pivot point. As the arm moves toward the handle, the lower front edge of a pawl engages the ratchet teeth on the plungers, there causing the plungers to simultaneously advance. These applicator guns can provide an effective system for dispensing highly viscous resin materials. The applicator guns increase the mechanical advantage of the operator. This allows the operator to hold the gun in various orientations and dispense the material in difficult to reach areas of a patient's oral cavity. However, such applicator guns have several disadvantages including their added bulk, complexity of operation, and relatively high cost to manufacture.
In view of the drawbacks with some conventional dispensing devices for dental materials, there is a need in the industry for an improved dispensing device. Particularly, the syringe device should be capable of dispensing two components of a dental composition simultaneously and in precisely metered quantities. In addition, a dental professional should be able to handle and use the syringe easily. A user should not be required to spend a large block of time loading the components into the barrels, mixing, and dispensing them accordingly. The dispensing mechanism should be relatively simple and not require the interaction of many small parts. The syringe should be economically feasible to manufacture. Moreover, the syringe should have a dispensing mechanism, which provide a mechanical advantage to the user. Such a syringe would be particularly valuable to users who need ergonomic assistance in dispensing the material from the syringe. The present invention provides a dispensing syringe having the foregoing features and characteristics. These and other objects, benefits, and advantages of this invention are evident from the following description and illustrated embodiments.